It's called Red Goddess. An open-world side-scrolling action-adventure (or metroidvania, if you prefer) where you play a young goddess named Divine, taking her on a journey across a planet controlled by her subconscious. This translates to a dangerous but gorgeous alien landscape. Like this:

"Split personalities" here means that you can turn into a more aggressive fire-being called Nar, or a more sneaky ice-being called Syn. Both are aspects of Divine's personality—her rage and her fear, respectively—along with the game's enemies, which are her "negative thoughts rebelling against her." Makes sense, considering the planet you're on resides in Divine's mind, where you search for lost memories to reveal an unknown threat.

Red Goddess has an ongoing but fully funded Kickstarter campaign. Check it our for more details, shots, videos and an early demo. As for the full game, look for it early next year on PC, PS Vita, PS4, and Wii U.